Generally, an electrophotographic process performs at least a cleaning process, an electric charging process, an exposure process, a development process, and a transfer process on an electrophotographic photoreceptor. These processes use a cleaning blade for removing remaining toner from the surface of a photosensitive drum to clean the surface, an electrically conductive roller for uniformly electrically charging the photoreceptor, a transfer belt for transfer of a toner image, etc. In view of plastic deformation and wear resistance, the cleaning blade is formed primarily of thermosetting polyurethane resin.
However, for example, in the case of use of a cleaning blade formed of polyurethane resin, a friction coefficient between a blade member and the photosensitive drum increases, and, in some cases, causing the following problems: the blade is turned up; the blade produces unusual noise; and a driving torque for the photosensitive drum must be increased. Also, in some cases, the following problem has occurred: the distal end of the cleaning blade is caught by the photosensitive drum, etc., to be stretched and cut, and is abrasively broken. These problems have been particularly marked in the case of a cleaning blade having low hardness; as a result, in some cases, the durability of the cleaning blade has been insufficient.
In order to solve these problems, conventionally, imparting high hardness and low friction to a contact portion of a polyurethane blade has been attempted. For example, the following method (refer to, for example, Patent Documents 1 to 3) has been proposed: the polyurethane blade is impregnated with an isocyanate compound for reacting a polyurethane resin and an isocyanate compound with each other such that high hardness is imparted only to the surface of the polyurethane resin blade and its vicinity, and low friction is imparted to the surface.
However, in order to impart required properties to the blade by the methods disclosed in Patent Documents 1 to 3, a polyurethane resin must be impregnated with a surface treatment liquid which contains an isocyanate compound at high concentration; accordingly, a surface-treated layer must be formed deep. An attempt to use a high-concentration surface treatment liquid and form the surface-treated layer deep involves a problem in that excess isocyanate is apt to remain on the blade surface; thus, a step of removing the excess isocyanate is required. By contrast, forming the surface-treated layer thin results in insufficient wear resistance, causing a problem of deterioration in cleaning performance.